Image Encryption and Decryption Using Chua’s Circuits

Abstract

Although chaos is interpreted as random in nature, it is actually deterministic. This very useful property can be used to encrypt signals. In this paper, Chua’s circuit is used to generate random sequences based on initial conditions; these sequences are then used to encrypt and decrypt an image. The key is encrypted using a function with a modulus operation, then used to initialize the Chua circuit. The output of the Chua circuit is three arrays X, Y, and Z. The encryption process can be divided into two steps. First, one sequence from the Chua circuit is used to form a 2D array; the other two sequences form another 2D array where both have the same size. Then, the result is XORed with the image to be encrypted and the rows and the columns are swapped horizontally and vertically. Second, the other matrix formed using the X–Y arrays after a modulus operation is used as an index for the image processed in the first step. Simulation results show that the scheme is sensitive to changes in the encryption parameters; a single incorrect parameter causes decryption to fail. This method’s strength therefore lies in the myriad unique factors required to generate the chaotic sequences, such that the images are very difficult to decrypt. Keywords: Chaos,